<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>02-结构伪类_01</title>
    <style>
        /* span元素 并且它是父元素中的第3个子元素 */
        /* an + b, a = 0, b = 3*/
        span:nth-child(3) {
            color: red;
        }
    </style>
</head>
<body>

<div>
    <p>p1</p>
    <span>span1</span>
    <span>span2</span>
    <span>span3</span>
    <span>span4</span>
    <span>span5</span>
</div>

</body>
</html>